1. Field of the Invention
The present invention relates to an image recording apparatus for recording an image using solid-state recording elements.
2. Description of the Related Art
Image recording apparatuses for recording an image on a recording medium by driving respective elements of a solid-state-recording-element array head, in which, for example, thousands of light-emitting elements or heating elements are arranged in the form of an array, in accordance with image data have been well known. Since each of such solid-state recording elements has its peculiar recording characteristic, nonuniformity in density may occur in an image recorded by the elements. For example, when using thousands of light-emitting elements, all the elements do not always emit light with the same intensity even if they are driven by the same driving current. Accordingly, various attempts have been made in order to correct the recording characteristics of the solid-state recording elements.
In one approach, the recording characteristics of respective recording elements are measured in the device manufacturing process, and different correction data for the respective recording elements provided based on the measured characteristics are stored in order to perform appropriate correction when forming an image. However, the characteristics of the solid-state recording elements gradually change with the lapse of time. In order to deal with such changes with the lapse of time, it is desirable that the correction data can be easily changed by the user and correction corresponding to the latest recording characteristics of the solid-state recording elements is always performed.
For example, a technique for satisfying such requirements is described in Japanese Patent Laid-Open Application (Kokai) No. 5-42682 (1993). That is, in a copying system including an image reading unit and an image recording unit, a test pattern is recorded by driving solid-state recording elements, and correction data for each of the solid-state recording elements is changed by reading the test pattern by the image recording unit and detecting the density of a pixel recorded by each element. Since these operations can be easily performed by the user, changes in the recording characteristics of the respective recording elements with the lapse of time can be sufficiently dealt with.
However, for example, when applying the above-described technique to a so-called full-line-type solid-state-recording-element array head in which thousands of solid-state recording elements are arranged in the form of an array, various problems will arise. That is, even if the solid-state recording elements of the image recording unit and the reading elements of the image reading unit are arranged at the same density, the recording elements and the reading elements are not always in a 1:1 relationship due, for example, to error in the magnification of the optical system of the image reading unit, and inaccuracy in driving of a motor for driving the reading head comprising the reading elements or an automatic original-feeder. Hence, it is impossible, in some cases, to exactly detect the density of the pixel recorded by each recording element on the test pattern. If correspondence between the density read by each reading element and the corresponding recording element deviates, and correction data is changed based on the density detected in the deviated state, correction will become meaningless or even enhance nonuniformity in the density.
The present invention has been made in consideration of the above-described problems.
It is an object of the present invention to provide an image recording apparatus which can accurately acquire the recording characteristics of solid-state recording elements so as to follow changes in the recording characteristics with the lapse of time, and which can prevent nonuniformity in the density in a formed image due to variations in the recording characteristics.
According to one aspect, the present invention relates to an image recording apparatus including at least one recording head, in which a plurality of solid-state recording elements are arranged, for performing image recording by causing each of the plurality of solid-state recording elements to record a pixel, and storage means for storing correction data for correcting image data in accordance with a recording characteristic of each of the plurality of solid-state recording elements so as to correspond to the corresponding one of the plurality of solid-state recording elements. Each of the plurality of solid-state recording elements is driven in accordance with input image data and the correction data stored in the storage means. The apparatus also includes pattern-data generation means for generating predetermined pattern data, and for causing each of a predetermined number of consecutive elements from among the plurality of solid-state recording elements to record a pixel, reading means for reading a test pattern recorded by the recording head based on the pattern data generated by the pattern-data generation means, acquisition means for acquiring the recording characteristic of each of the plurality of solid-state recording elements based on a ratio of a number of solid-state recording elements which have recorded pixels in accordance with the predetermined test pattern to a number of pixels of the test pattern read by the reading means, and changing means for changing the correction data for each of the solid-state recording elements in accordance with the recording characteristic of the corresponding one of the solid-state recording elements acquired by the acquisition means.
According to another aspect, the present invention relates to a method for adjusting an image recording apparatus including at least one recording head, in which a plurality of solid-state recording elements are arranged, for performing image recording by causing each of the plurality of solid-state recording elements to record a pixel, and storage means for storing correction data for correcting image data in accordance with a recording characteristic of each of the plurality of solid-state recording elements so as to correspond to the corresponding one of the plurality of solid-state recording elements. Each of the plurality of solid-state recording elements is driven in accordance with input image data and the correction data stored in the storage means. The method includes a pattern-data generation step of generating predetermined pattern data, and causing each of a predetermined number of consecutive solid-state recording elements from among the plurality of solid-state recording elements to record a pixel based on the predetermined pattern data, a reading step of reading a test pattern recorded by the recording head based on the pattern data generated in the pattern-data generation step, an acquisition step of acquiring the recording characteristics of each of the plurality of solid-state recording elements based on a ratio of a number of solid-state recording elements which have recorded pixels in accordance with the predetermined test pattern to a number of pixels of the test pattern read in the reading step, and a changing step of changing the correction data for each of the solid-state recording elements in accordance with the recording characteristic of the corresponding one of the solid-state recording elements acquired in the acquisition step.
According to still another aspect, the present invention relates to a copying system including reading means for reading an original and outputting image data, at least one recording head, in which a plurality of solid-state recording elements are arranged, for performing image recorded by causing each of the plurality of solid-state recording elements to record a pixel, and storage means for storing correction data for correcting image data in accordance with a recording characteristic of each of the plurality of solid-state recording elements so as to correspond to the corresponding one of the plurality of solid-state recording elements. Each of the plurality of solid-state recording elements is driven in accordance with the image data output from the reading means and the correction data stored in the storage means. The system also includes pattern-data generation means for generating predetermined pattern data, and for causing each of a predetermined number of consecutive solid-state recording elements from among the plurality of solid-state recording elements to record a pixel, acquisition means for causing the reading means to read a test pattern recorded by the recording head based on the pattern data generated by the pattern-data generation means, and for acquiring the recording characteristic of each of the plurality of solid-state recording elements based on a ratio of a number of solid-state recording elements which have recorded pixels in accordance with the predetermined test pattern to a number of pixels of the test pattern read by the reading means, and changing means for changing the correction data for each of the solid-state recording elements in accordance with the recording characteristics of the corresponding one of the solid-state recording elements acquired by the acquisition means.